1. Field of the Invention
This invention relates to a reversible direction capsule chemistry sample liquid analysis system and method which, although suitable for application to a wide variety of analyses on a wide variety of sample liquids, are particularly adapted to the automated clinical analyses in turn of pluralities of human biological sample liquids.
2. Description of the Prior Art
Although a variety of capsule chemistry sample liquid analysis systems and methods are known in the prior art, none are known which operate through repeatedly reversible, bi-directional flow of a sample liquids stream to enable repeated, precisely timed analyses of each of the stream-contained sample liquids at frequent intervals by one or each of more than one sample liquids analysis means; nor are any of these prior art capsule chemistry systems and methods known which utilize highly precise positive displacement pumping at the inlet, or both the inlet and outlet, ends of the system to provide for highly precise formation of the sample liquids stream, and highly precise flow of the same through the system.
More specifically, the most relevant of these prior art capsule chemistry sample liquids analysis systems and methods may be understood to be those disclosed in U.S. Pat. No. 4,853,336 issued Aug. 1, 1989 to Stephen Saros, et al, and assigned to the predecessor in interest of the assignee hereof, wherein a sample liquids stream containing successive sample liquid capsules, or test packages, is formed in a first conduit section, passed through an enlarged second conduit section for merger and reaction of included sample and reagent liquid test package segments, and passed through a third conduit section which includes a plurality of spaced sample liquids analysis means, for example colorimetric flow cells, for successive colorimetric analyses of the thusly merged sample and reagent liquid segments with regard to the progress and completion of the sample and reagent liquid segments reactions in each instance. Since flow of the sample liquids stream is this prior art system is conventionally uni-directional, it will be immediately understood by those skilled in this art that a separate and distinct flow cell will be required in the third conduit section for each successive analysis of each of the reacted sample and reagent liquid segments in turn, and that each of such flow cells will be limited to but a single analysis of each of those segments. This, of course, adds to the cost and complexity of this prior art sample liquid analysis system, can detract from the overall reliability thereof, and adds two sample liquid carryover-intensive conduit-flow cell junctures to the system for each additional flow cell. Also, there is, of course, as a practical matter, a limit to the number of flow cells which can be realistically incorporated in a sample liquid analysis system of this nature; it being clear, for example, that the use of sixteen serially arranged flow cells in the third conduit section, to provide sixteen readings on the progress to completion of each of the sample and reagent liquid segments reactions as may be desired, or even required by the particularly stringent demands of current highly sophisticated clinical chemistries, would most probably far exceed that limit.
In addition, although this Saros, et al prior art capsule chemistry system does utilize positive displacement pumping, taking the form of a peristaltic pump, in the formation and flow of the sample liquids stream, that pump is located at the "back" or outlet end of the system to result in a lesser degree of precision in stream formation and flow than that achievable with "front" end pump location since, as will be immediately understood by those skilled in this art, the pressure at the aspiration port does not depend, in the latter case, on the pressure drop along the system. Also, peristaltic pumps are subject to eventual reduction in overall precision of operation due to normal degredation over time in the structural integrity and elasticity of the peristaltic pump tubes. Further, certain applications of this prior art capsule chemistry system have been found to require the incorporation of one or more mixing coils in the third conduit section to promote the required very thorough mixing of the sample and reagent liquid segments in turn, and the reaction therebetween, prior to the flow of the sample liquids stream through the analysis means; and this also adds to the cost and complexity of the system, and again introduces two sample liquid carryover-intensive conduit-mixing coil junctures to the system for each such mixing coil, and of course, introduces some element of undesirable backpressure to the sample liquids stream for each mixing coil.
Another prior art system of interest, but of more limited relevance, is the sample liquids analysis system disclosed in U.S. Pat. No. 4,253,846 issued Mar. 3, 1981 to William J. Smythe, et al, and assigned to the predecessor in interest of the assignee hereof, wherein a plurality of discrete reagent liquids are selectively introducable through injection valves into a stream of successive discrete sample liquid segments flowing in a conduit for sample and reagent liquids reaction and subsequent analysis by a single analysis means, again for example a colorimeter flow cell. Sample liquids stream flow in this prior art system is again uni-directional; and this combined with the use of but a single sample liquids analysis means, of course limits the system to but a single analysis on each of the discrete sample liquid segments in turn.